Enumeration and Isolation of the Human Gut Using Manual and Automated Methods of Streaking Inoculated Media

Darryl Gopaul, Leslie Hart, Brenda Cupp, Martin Lee
St. Joseph's Health Centre London, Ontario Canada and Great Smokies Diagnostic Laboratory, Asheville, North Carolina, USA

Colonizing bacteria in the human gut are necessary in the metabolism of nutrients and food components. One of bacteria's key roles for example, is the digestion of soluble fibers to short chain fatty acids. The numbers and types of organisms present in the stools of humans is of interest in patients with diagnosis of food allergies, malabsorption syndrome, autoimmune disease and in acute and chronic gastrointestinal dysfunction. The purpose of this study was to evaluate the recovery of fecal bacteria by the manual method of plating stools compared to the automated method of spreading stools onto selective media. A total of 15,234 stools were streaked in 1993-1994 using the manual method and 16,923 stools were streaked in 1994-1995 using an automated method (Vista Laboratories Ltd. ISOPLATER). The number of isolates considered potentially pathogenic recovered by the manual method was 5,921 while the number recovered using the ISOPLATER was 9,359 (p<0.001). A significant increase was noted in the recovery of certain organisms: Klebsiella pneumoniae-mucoid strains (13.6% to 20.1%), Aeromonas (0.08% to 0.2%), Proteus vulgaris (1.1% to 1.8%), non-Lactose fermenting E. Coli (0.6% to 0.9%), Pseudomonas (3.7% to 6.5%), Shigella (0.007% to 0.03%), Campylobacter (0.007% to 0.02%), Yersinia (0% to 0.06%), and Vibrio (none to 0.02%) using the ISOPLATER. While one could argue that the increased recovery reflects year-to-year variation, the large number of specimens evaluated suggests that the ISOPLATER automated streaker leads to improved recovery of fecal bacteria as compared to the manual method.

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Evaluation of the isoplater 180 for automated primary plating of clinical specimens

M. Valsorda, P. Lebel, J.-R. LaPointe, L. Kemp, C. Laferriére, «Hôpital Sainte-Justine» and «Université de Montréal»


The ISOPLATER is designed to automate and standardize the streaking of Petri dishes. We have evaluated the ISOPLATER in a large pediatric microbiology laboratory, comparing its automated streaking to the standard manual method.

Two hundred ten specimens were set up both by ISOPLATER and manual methods, using standardized inocula on paired plates incubated indentically: 99 urines (of which 15 were positive), 31 throat swabs, 19 vaginal secretions, 18 sputa, 18 stools, 18 pus, and 10 blood cultures. Incubation was done aerobically and anaerobically as needed by the specimen type.

No differences were observed on paired plates regarding: colony, morphology or numbers, spreading, isolated colonies, background flora, or contamination. Colony sizes were smaller and zones of hemolysis less well-defined on the plates streaked by the ISOPLATER when incubated in air, but no differences were observed when paired plates were incubated in CO2. Streaking delayed up to 30 minutes after inoculation did not change the final results of the culture, as evaluated in 12 urine and 8 throat cultures.

We conculde that the ISOPLATER gave results comparable to those of conventional manual streaking fora good variety of clinical specimens. The automatic streaker was easy to use, reliable and well-accepted by the technologists.